Reactive power control device, reactive power control method, and reactive power control program

Abstract

A reactive power control device includes a voltage acquisition unit that detects a grid voltage and a DC voltage; a modulation rate calculation unit that calculates a modulation rate; a reactive power command acquisition unit that obtains a first reactive power command from a host device; a blind zone determination unit that determines whether the first reactive power command is at a blind zone level; a reactive power command calculation unit that limits or compensates the first reactive power command according to the modulation rate and calculates a second reactive power command when the blind zone determination unit determines that the first reactive power command is not at the blind zone level; and a reactive power command output unit that outputs the second reactive power command when the second reactive power command is calculated, and outputs the first reactive power command when the second reactive power command is not calculated.

The invention claimed is: 
     
         1 . A reactive power control device comprising:
 a voltage acquisition unit that detects a grid voltage and a DC voltage;   a modulation rate calculation unit that calculates a modulation rate using the grid voltage and the DC voltage obtained by the voltage acquisition unit;   a reactive power command acquisition unit that obtains a first reactive power command from a host device;   a blind zone determination unit that determines whether the first reactive power command obtained by the reactive power command acquisition unit is at a blind zone level;   a reactive power command calculation unit that limits or compensates the first reactive power command according to the modulation rate calculated by the modulation rate calculation unit and calculates a second reactive power command when the blind zone determination unit determines that the first reactive power command is not at the blind zone level; and   a reactive power command output unit that outputs the second reactive power command when the second reactive power command is calculated by the reactive power command calculation unit, and outputs the first reactive power command when the second reactive power command is not calculated by the reactive power command calculation unit.   
     
     
         2 . The reactive power control device according to  claim 1 , further comprising a command value polarity determination unit that determines whether the first reactive power command obtained by the reactive power command acquisition unit is greater than 0, wherein
 the reactive power command calculation unit calculates the second reactive power command by limiting the first reactive power command in an inductive region when the command value polarity determination unit determines that the first reactive power command is greater than 0, and calculates the second reactive power command by limiting the first reactive power command in a capacitive region when the first reactive power command is determined to be less than 0.   
     
     
         3 . The reactive power control device according to  claim 1 , wherein the reactive power command calculation unit starts limiting the first reactive power command when the modulation rate exceeds a predetermined limitation start level, and terminates limiting the first reactive power command when the modulation rate exceeds a predetermined limitation end level. 
     
     
         4 . The reactive power control device according to  claim 1 , further comprising a storage in which a modulation rate compensation gain according to the modulation rate is stored as a table, wherein
 the reactive power command calculation unit refers to the table stored in the storage to extract the modulation rate compensation gain according to the modulation rate, and multiplies the extracted modulation rate compensation gain by the first reactive power command to limit or compensate the first reactive power command, thereby calculating the second reactive power command.   
     
     
         5 . The reactive power control device according to  claim 1 , further comprising a storage in which a predetermined modulation rate reference is stored, wherein
 the reactive power command calculation unit calculates a difference or a deviation between the modulation rate reference stored in the storage and the modulation rate, performs PI control on the calculated difference or deviation, and adds a control amount determined by the PI control to the first reactive power command to limit or compensate the first reactive power command, thereby calculating the second reactive power command.   
     
     
         6 . A reactive power control method comprising:
 a voltage acquisition step of detecting a grid voltage and a DC voltage;   a modulation rate calculation step of calculating a modulation rate using the grid voltage and the DC voltage obtained by the voltage acquisition step;   a reactive power command acquisition step of obtaining a first reactive power command from a host device;   a blind zone determination step of determining whether the first reactive power command obtained by the reactive power command acquisition step is at a blind zone level;   a reactive power command calculation step of limiting or compensating the first reactive power command according to the modulation rate calculated by the modulation rate calculation step and calculating a second reactive power command when the blind zone determination step determines that the first reactive power command is not at the blind zone level; and   a reactive power command output step of outputting the second reactive power command when the second reactive power command is calculated by the reactive power command calculation step, and outputting the first reactive power command when the second reactive power command is not calculated by the reactive power command calculation step.   
     
     
         7 . A non-transitory computer-readable storage medium storing a reactive power control program that causes a computer to execute processing for the reactive power control method according to  claim 6 .